Congenital tibial pseudarthrosis

　　1. Etiology

　　The etiology of congenital tibial pseudarthrosis is not fully understood at present, and there are many theories, such as intrauterine injury theory, vascular malformation and metabolic disorder theory, etc., but these have been abandoned. Currently, the most widely accepted ones are the following three:

　　1. Theory of Neurofibroma:Congenital tibial pseudarthrosis is caused by intraosseous and extraosseous neurofibroma tissue, which leads to the normal development disorder of local bone quality and also affects the repair of fractures, thereby causing pseudarthrosis. Among the 14 cases of congenital tibial pseudarthrosis reported by Boyd, 9 had neurofibroma nodules and skin pigmentation spots, and 17 out of 178 cases had this condition. Some individual cases also showed some changes in the posterior tibial nerve. The 9 cases of congenital tibial pseudarthrosis observed in Tianjin Hospital had many similarities with neurofibroma, and the microscopic examination of some cases at the pseudarthrosis site also conformed to neurofibroma. There is undoubtedly a relatively close relationship between these two diseases.

　　2, Fibrous Dysplasia Theory:Boyd and Sage (1958) reported 15 cases, including two cases with false joints showing the appearance of fibrous dysplasia under the microscope, mentioning the relationship with the disease. Most cases have brown spots on the skin, and at the early stage of pseudarthrosis, the bone in the cystic change area is curved and deformed. In some cases, the clitoris is larger, resembling the third type of fibrous dysplasia, Albright's disease. X-ray manifestations show that the early cystic change area or the remaining cystic change area of the pseudarthrosis is glassy, and the cancellous bone disappears, similar to fibrous dysplasia. More importantly, the local pathological changes are also quite similar. From the above relationship, there is also a closer relationship between the two.

　　3, Neurotic Theory:Aegerter (1995) proposed that neurofibromatosis, fibrous dysplasia, and congenital tibial pseudarthrosis have many similarities, and may be caused by a common cause leading to fibrous tissue dysplastic proliferation. The malformation and disorder of these fibrous tissues make the normal growth and maturation of bone in the local area appear incompetent. The cause of this change may be abnormal local nerve pathways. In Moore's study of 78 congenital malformation cases, 91% of the cases had pathological changes in the peripheral nerves, which supports this neurotic theory.

　　Two, pathogenesis

　　Many scholars believe that congenital tibial pseudarthrosis is related to neurofibromatosis, as patients may have typical neurofibromatous subcutaneous nodules on the skin simultaneously. These fibroblastic masses are due to changes in the nerve pathways in the region, resulting in abnormal growth. The pseudarthrosis site often has thickened periosteum and a very thick fibrous tissue sheath. McElvenny believes that this dysplastic proliferation of soft tissue will hinder bone formation and the normal growth of callus. The thick fibrous ring compresses the bone tissue, reduces its blood supply, and causes osteoporosis. According to Boyd's pathological observations, the pathological changes in type II are considered to be an invasive osteolytic fibroma. The younger the patient, the more aggressive the invasion. As age increases, the invasiveness decreases, and by the time the epiphysis closes, this fibroma loses its invasiveness. Therefore, even if osseous union occurs during the growth period, pseudarthrosis may still occur. Therefore, a conclusion of cure should not be easily made before puberty.

　　One, complications caused by the disease itself

　　Once a false joint is formed, the child cannot bear weight while walking, and the longer the time, the more severe the symptoms become. The deformity of the lower leg may worsen, sometimes presenting as a 'flail-like' appearance. Fractures often occur repeatedly during adolescence, and in some cases, infection may occur due to the fractured end piercing the skin.

　　Secondly, postoperative complications

　　1, Since the children with this disease require general anesthesia during treatment, nausea and vomiting often occur after general anesthesia. The longer the anesthesia time, the higher the incidence of vomiting. Therefore, the child should be placed in a supine position with the head turned to one side before the child wakes up from general anesthesia to prevent aspiration due to vomiting.

　　2, Children have poor tolerance to blood loss, and when blood loss is excessive, they often appear pale, with more bleeding from the wound. At this time, timely symptomatic treatment should be given.

　　Firstly, according to the shape of the tibia, the clinical classification is generally divided into three types

　　1, Curvature type:After birth, the lower segment of the tibia is curved forward, but there is no pseudarthrosis. The cortex at the anterior bow of the tibia thickens, the medullary cavity is occluded, the tibial ends atrophy and harden, presenting a bow shape. After fracture, local non-union occurs after general treatment, forming a pseudarthrosis, or due to the lack of recognition of this disease, an osteotomy operation is performed rashly, resulting in non-union, continuing to develop and the two ends are absorbed, the bone ends harden, the distal end further atrophies and thins, presenting as a pen-point shape.

　　2, Cystic type:After birth, there is a cystic change in the middle and lower third of the tibia, but the shaft is not thin, and it is not easy to be discovered clinically. Fractures occur after minor trauma, resulting in non-union and subsequent pseudarthrosis.

　　3, Pseudarthrosis type:Defects in the middle and lower segments of the tibia are found immediately after birth, forming pseudarthrosis. There is a relatively hard fibrous tissue or cartilage connection at the pseudarthrosis site. The bone ends become thinner and atrophy with growth and development, more pronounced at the distal end, presenting as a pen-point shape. The cortex is thin, and sometimes the surrounding soft tissues also atrophy, including the gastrocnemius muscle. If the fibula is involved, similar changes occur.

　　Secondly, there is another classification method, where Boyd divides this condition into six types

　　1, Type I:Pseudarthrosis occurs simultaneously with a precurvature, with a partial absence of the tibia at birth, and there may be other congenital malformations.

　　2, Type II:Pseudarthrosis occurs simultaneously with a precurvature, with a葫芦状 narrowing of the tibia at birth. There may be spontaneous fractures or fractures caused by minor injuries before the age of 2, collectively referred to as high-risk tibial fractures. The bone is cone-shaped, round, and hard, with occlusion of the medullary cavity. This type is the most common, often accompanied by neurofibromatosis, with the worst prognosis. Fracture recurrence is common during growth, and the number of fractures will decrease as age increases, and fractures will no longer occur after the epiphyses mature.

　　3, Type III:Pseudarthrosis occurs within congenital cysts, usually at the junction of the middle and lower third of the tibia. There may be a precurvature followed by fracture, and the chance of fracture after treatment is less than that of Type II.

　　4, Type IV:There is a hardening segment at the junction of the middle and lower third of the tibia, and pseudarthrosis occurs, with partial or complete occlusion of the medullary cavity. Incomplete fractures or marching fractures may occur in the tibial cortex. After the fracture breaks, it will not heal again, and the fracture site will widen to form a pseudarthrosis. This type of fracture has a better prognosis, and treatment before the fracture matures is more effective.

　　5, Type V:In cases of tibial dysplasia, pseudarthrosis may occur in the tibia, and pseudarthrosis in both bones can occur simultaneously. If the lesion is limited to the fibula, the prognosis is better. If the lesion progresses to form a tibial pseudarthrosis, its development process is similar to Type II.

　　6, Type VI:Pseudarthrosis caused by intramedullary nerve sheath tumors or Schwannomas is rare, and the prognosis depends on the invasiveness of the intramedullary lesion and the treatment.

　　This disease is a congenital disease with no effective preventive measures. Early diagnosis and early treatment are the key to the prevention and treatment of the disease. However, attention should be paid to the fact that the treatment methods vary from person to person and cannot be uniform; conservative therapy is preferred for infants and young children, and it is not advisable to perform osteotomy and deformity correction easily, or to take pathological or early scraping and bone grafting. Overly aggressive surgical treatment will lead to serious consequences.

　　This disease mainly involves X-ray examination: X-ray films show anterior curvature, angular deformation, fibrous cystic change, pseudo-joint formation, bone ends becoming slender and conical, bone ends becoming ossified and medullary cavity occlusion, bone cortex becoming thin, bone atrophy, the distal tibial joint surface may be变形, the fibula may also have pseudo-joint changes or deformity, lower limb shortening. If necessary, CT or MRI examination can be chosen as a supplement.

　　Patients with congenital tibial pseudo-joint generally have no special dietary requirements, but it is recommended that the dietary principles for patients be light, with an emphasis on eating more vegetables and fruits, supplementing vitamins, and reasonably matching the diet to ensure nutritional balance.

　　First, treatment

　　1. Treatment

　　In summary, the treatment of this disease is still a difficult problem to this day. Many surgical methods can be adopted, such as large-bone external bone grafting, composite tissue flap transplantation, bridging bone grafting, and double external bone grafting, but the results are all unsatisfactory, often resulting in bone graft absorption and recurrence of fracture. With the development of microsurgery, vascularized fibula transplantation or fibula transfer with vascular pedicle has been started, which has improved local blood supply and improved the efficacy of this disease. However, the long-term effects are still to be summarized.

　　(1) During the treatment process, repeated surgery multiple times does not achieve the effect of fracture healing, resulting in lower limb shortening, and possibly leading to disability including amputation. This point must be fully explained to the parents of the child.

　　(2) It is contraindicated to perform surgical correction for deformity in those who have not formed a pseudo-joint but only have tibial curvature. Once surgery is performed, it will inevitably lead to the formation of a pseudo-joint, causing unimaginable consequences.

　　(3) For those who have not formed a pseudo-joint but only have tibial curvature, surgical correction of the deformity is contraindicated. Once surgery is performed, it will inevitably lead to the formation of a pseudo-joint, causing unimaginable consequences. If the tibia has anterior and external curvature and severe sclerosis, the periosteum of the lesion should be thoroughly removed, and autologous bone grafting and fixation should be performed. At the same time, a strong external fixation is necessary to achieve satisfactory results.

　　(4) For those who have formed a pseudo-joint, surgery is more suitable after 6 to 7 years old, as the bones of older children are thicker and harder than those of young children. During surgery, enough cancellous bone and a sufficient length of bone plate can be taken to ensure fracture healing. During the waiting period for surgery, a brace with a definite effect should be used to protect against further bending and fracture occurrence. For those with better bone healing conditions, surgery can also be performed as soon as possible.

　　2. Several commonly used surgeries

　　(1) Boyd surgery: This surgery uses the healthy tibia bone plate, peels off the periosteum on it, leaves part of the cancellous bone, and fixes the healthy tibia bone plate at the artificial joint site with it. Then, cancellous bone is taken from the ilium and transplanted to fix it.

　　(2) Sofield surgery: This operation is suitable for patients with short tibia at the distal end of the tibial artificial joint. Make a longitudinal incision on the anterior side of the tibia, expose the upper and lower ends of the tibial artificial joint, and completely resect the soft tissue and bone of the upper and lower ends of the tibial artificial joint, paying attention not to damage the epiphysis at the lower end of the tibia. Enlarge the medullary cavity, cut the tibia at the upper end, turn the cut tibia upside down, align the upper end with the distal end of the tibia, and fix it with an intramedullary nail. If there is a gap in the middle of the tibia, take the contralateral fibula for bone grafting to make the upper and lower ends closely contact and apply a certain amount of pressure. Suture the periosteum, subcutaneous tissue, and skin. Apply a long leg cast for fixation for 3-6 months after surgery, but it can bear weight to stimulate bone growth during this period.

　　(3) Free Fibula Transplantation: In recent years, due to the development of microsurgery, the application of free fibula with vascular pedicle has achieved certain effects. This operation requires to be performed under a surgical microscope and can only be completed with the participation of professional microsurgeons. The operation age is between 6 and 7 years, with a higher success rate, and the success rate of surgery in young patients is lower. Maintaining the patency of the vascular anastomosis is the key to the success of the operation.

　　(4) Ilizarov one-time compression and one-time extension surgery: completely resect the diseased part of the artificial joint, including the ossified bone, the fibrous tissue between the artificial joint, and the diseased periosteum, and try to expose the medullary cavity as much as possible. Remove the cancellous bone block from the child's ilium, cut it into bone chips and strips, insert the strips into the medullary cavity, and implant a few bone chips around it. Apply Ilizarov external fixation frame end-to-end compression fixation, and place another Ilizarov external fixation frame above the artificial joint to perform diaphyseal corticotomy on the shortening limb. Begin to extend 0.5-1mm per day starting on the 7th day after surgery, which can be done in 2-4 times, 0.25mm each time, but not too quickly, otherwise it may cause non-union. Generally, it can be extended by 4-12mm. Stop extending when the required extension length is reached, and the artificial joint is completely healed before the external fixation device can be removed.

　　II. Prognosis

　　The treatment of this disease is still a difficult problem to this day, with many treatment methods, but the effects are all unsatisfactory.